Belgian Pat. No. 868,875 to Ishihara Sangyo Kaisha Ltd. discloses and claims a number of 4-(5-trifluoromethyl-2-pyridyloxy)phenoxy alkanoic acids and their derivatives as well as their use as herbicides in broad-leaved crops.
British Pat. No. 1,550,574 to Ciba Geigy AG discloses and claims a number of pyridyloxphenoxy propionic acid compounds and their herbicidal use. This reference teaches the use of such compounds as plant growth regulators, as for controlling tobacco sucker growth.
Other pyridyloxyphenoxy propionic acid products and methods are disclosed in copending application Ser. No. 817,943 filed July 22, 1977 corresponding to European Patent Application 483 and in copending applications PCT/US 80/00956 and PCT/US 80/01018 filed July 30, 1980.
U.S. Pat. No. 3,816,092, issued June 11, 1974, teaches the selective control of weeds in a variety of crops, including rice. This reference teaches at Col. 1, lines 42-45, that herbicidally active agents cannot be predicted from the prior knowledge of compounds that have herbicidal activity.
The principal weed of rice is an annual grass, Echinochloa crusgalli. This grass and its close relatives are troublesome weeds in many countries of the world. Although a number of chemicals and techniques have been developed to attack this problem, there has not yet been a completely acceptable method for controlling such grassy weeds in the presence of desirable crops such as rice.